// @(#)ParetoDistribution.java   5/2003
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package drcl.util.random;

import java.awt.*;
import java.util.*;

/**
 * This class implements a pareto distribution.
 * Parameters: scale, shape
*/

public class ParetoDistribution extends RandomNumberGenerator
{
  public String   getName()           { return "Pareto Distribution"; }

  public ParetoDistribution (double scale_, double shape_)
  { this(scale_, shape_, 0L); }

  public ParetoDistribution (double scale_, double shape_, long seed_)
  {
    this(seed_);
    scale = scale_;
    shape = -1.0 / shape_;
  }
  
  double scale = 1.0;
  double shape = - 1.0;
  
  public ParetoDistribution()
  { super(); }

  public ParetoDistribution(long seed_)
  { super(seed_); }
  
  public double getMean()
  { return scale / (1 + shape); }

  public double nextDouble()
  {
    double x;
    
    do { x= r.nextDouble(); } while (x == 0.0);

    // Mapping from Uniform to Pareto
    return scale * Math.pow(x, shape); 
  }

  public int  nextInt()
  {  return (int) nextDouble();  }

  public long nextLong()
  {  return (long) nextDouble();  }

  public void setScale(double scale_)
  { scale = scale_; }

  public double getScale()
  { return scale; }
  
  public void setShape(double shape_)
  { shape = -1.0 / shape_; }

  public double getShape()
  { return -1.0 / shape; }

  public String info(String prefix_)
  {
    return super.info(prefix_)
      +  prefix_ + "Scale = " + scale + "\n"
      +  prefix_ + "Shape = " + getShape() + "\n";
  }

  public String oneline()
  {
    return super.oneline()
      + ", scale=" + scale
      + ", shape=" + getShape();
  }
}

